Correction: An earlier version of this article misquoted a Palestinian diplomat. In an appearance on CNN, Maen Rashid Areikat, the Palestine Liberation Organization’s chief representative to the United States, said, “We’re in the business of legitimizing a Palestinian state,” not “We’re in the business of legitimizing Palestinians.” This version has been corrected.

President Obama sought to reassure Israel and its supporters of “ironclad” U.S. support Sunday in a speech to a Jewish lobbying group that also warned that time could be running out for a peace accord with Palestinians.

Obama, wading afresh into a topic that evoked anger from Israeli leaders last week, insisted again that 1967 boundary lines should be the starting point for talks on a new Palestinian state. But he allowed that the dividing line would be negotiated to accommodate Israeli settlements and security needs.

“Israelis and Palestinians will negotiate a border that is different than the one that existed on June 4, 1967,” Obama told the American Israel Public Affairs Committee (AIPAC) at its annual conference in Washington.

Acknowledging that Israel faced “hard choices” and security risks, Obama argued that stalling on peace negotiations posed even greater dangers for the country’s survival. The Arab Spring movement and changing demographic forces — including growing numbers of Palestinians west of the Jordan River — present long-term challenges to Israel that will be resolved only by the creation of separate homelands for Jews and Palestinians, he said.

Meanwhile, Israel faces increasing political isolation as Palestinians press their demands for international recognition of a Palestinian state, Obama said.

“No matter how hard it may be to start meaningful negotiations under current circumstances, we must acknowledge that a failure to try is not an option,” he said. “The status quo is unsustainable.”

Reassurances

Obama also reiterated themes of unshakable support for Israel that brought loud applause from the packed auditorium of nearly 10,000. He affirmed U.S. opposition to a Palestinian plan to seek a vote in the U.N. General Assembly on Palestinian statehood in September. He vowed to help Israel defend itself, promising U.S. military assistance on missile defense and pledging to block Iranian nuclear aspirations. And he assailed a recent Palestinian unity agreement that elevated the stature of the Hamas movement, which the United States and Israel regard as a terrorist group.

“No country can be expected to negotiate with a terrorist organization sworn to its destruction,” he said.

Obama said he was not surprised by the uproar over his Thursday speech but added that “if there is controversy, it is not based on substance.”

“What I did on Thursday was to say publicly what has long been acknowledged privately,” he said. “I’ve done so because we can’t afford to wait another decade, or another two decades, or another three decades to achieve peace. The world is moving too fast. The extraordinary challenges facing Israel will only grow. Delay will undermine Israel’s security and the peace that the Israeli people deserve.”

While the president’s core message differed little, Obama appeared to have succeeded in easing the concerns of some Israelis who had sharply criticized his speech Thursday.

Israeli Prime Minister Binyamin Netanyahu, who met with Obama for more than two hours Friday, issued a statement saying he was “determined to work with President Obama to find ways to renew peace negotiations.”

“I share the president’s desire to advance peace and I appreciate his efforts, past and present, to achieve this goal,” Netanyahu said in a statement released by his office.

The Israeli leader, initially angered by Obama’s call for 1967 border lines as a starting point for negotiations, has since told aides that he is reassured about Obama’s intentions after their talks Friday.

A ‘positive change’

Josh Block, a former AIPAC spokesman who is a senior fellow at the Progressive Policy Institute, said Obama’s speech Sunday was a “strong reaffirmation of the U.S.-Israel relationship and represented an important and positive change” from his remarks Thursday.

“By adding a whole section to the speech that was missing on Thursday, President Obama put himself in line with presidents since Lyndon Johnson who have said again and again, Israel cannot go back to the 1949/1967 lines,” Block said. “This is an important and crucial change from what he said last week.”

Other Middle East experts said Obama had made important progress in linking the peace process with Israel’s future security.

“If this is the beginning of a move to publicly convince Israelis and AIPAC partisans about the importance of peace in the language that they best understand — i.e. security — then it’s a really good step,” said Joel Rubin, chief operating officer for the National Security Network, a progressive-leaning think tank.

A Palestinian official also expressed cautious support for the president’s remarks and appeared to offer hope that the push for a U.N. vote in September could be delayed if there is significant progress toward a peace settlement.

“We are not in the business of delegitimizing Israel. We’re in the business of legitimizing a Palestinian state,” Maen Rashid Areikat, a Palestinian diplomat and chief of the Palestine Liberation Organization’s delegation in Washington, said on CNN’s “State of the Union.”

Yet a key Arab advocate for Mideast peace said in remarks released Sunday that he had little hope for progress in the near future.

“My instincts tell me not to expect much over the next couple of months, unfortunately,” King Abdullah II of Jordan told ABC News’s “This Week” in an interview taped before Obama’s Thursday speech. “I just have a feeling that we’re going to be living with the status quo for 2011.”

Although questions about his Mideast policy are likely to linger, Obama will be tending to other allies during a weeklong trip to Ireland, England, France and Poland that begins late Sunday.